Conventionally, a metallic material such as Nb--Ge (for example, Nb.sub.3 Ge) and the like is used as a superconducting material. Because this material is a metal, it has high ductility, malleability, and flexure and can be used to construct a coil for use in a superconducting magnet and also a coil for use in an electrical accumulator coil.
However, the onset of the superconducting critical temperature (hereinafter referred to as Tc) of this metal is low, being only 23.degree. K. or lower. On the other hand, for industrial applications, it is extremely important that the Tc be 100.degree. K. or higher, and that the temperature where the electrical resistance becomes zero (hereinafter referred to as Tco) be 77.degree. K. or higher.
Recently, a copper oxide ceramic superconducting material has been attracting considerable attention as such a superconducting material. However, this copper oxide ceramic superconducting material is not necessarily adequate in ductility, malleability, and flexure. Also, there is a problem that processing the material after it is formed is extremely difficult.
For these reasons, no method is as yet known for preparing this copper oxide ceramic superconducting material for use in the form of a coil, nor is any structure with such a coil known wherein a cooling medium can be incorporated therein for cooling the material.